1. Field of the Invention
The present invention is directed to an improved non-slipping device adapted to prevent the back-sliding of skis and removably mounted onto a ski. Said non-slipping device contains a removable braking element fitted into fastening elements attachable to the ski, said braking element including a blade extending under the bottom surface of the ski. The braking element is kept in place with the aid of locking means movably arranged relative to said fastening elements whereby the up-turned sides of said braking element include short pivot pins directed towards each other and adapted to co-act with said fastening elements, said braking element in its attached position being biased by a spring in such a way that said blade in its braking position extends about perpendicularly downwards from the bottom surface of said ski and in its forward running position butts against said bottom surface.
2. Description of the Prior Art
It is a frequently occurring problem in cross-country skiiing that the skis glide equally well backwards as forward. This problem is especially noticeable with modern skis which have the bottoms made of well gliding synthetic material which normally need not be waxed at all.
The bottom surface of modern ski may include recesses and notches which are supposed to improve the gripping ability of the skis, but the value of which has been found to be limited.
Another possibility for improving the gripping ability is to use purely mechanical means. Various devices which press into the snow have been used. Such devices may consist of spike-shaped parts pressing straight downwards, similar to the safety brakes which prevent the free gliding of slalom skis, or they may have pivotally turning blade members which are biased into a downward direction by spring elements and which at the forward running motion of the skis swing to a direction essentially parallel with the bottom of the ski in order to allow for good forward glide.
The above mentioned spike-shaped non-slipping devices are generally complicated in structure. On hard snow such devices may work satisfactorily, but since such devices are often susceptible to impacts and moreover are easily filled with snow their utility is very restricted.
The kind of non-slipping devices having swinging braking elements generally include some kind of blades which are swung down at the sides of the skis. Such non-slipping devices are often mounted in such a way that they fairly easily may be removed when the condition allow. This kind of devices are described e.g. in CH Pat. No. 586 053 (Schwarz) and in SE Pat. No. 50 439 (Dahl). The greatest disadvantage with non-slipping devices which are mounted on, or which function on the sides of the skis is that in their effective position they extend fairly far out from the sides of the skis. From this reason they can seldom be used in good narrow tracks. The mechanical parts extending outside the skis form a risk of danger, since they may easily catch in the corresponding device on the other ski, in the snow, or in any obstacles at the side of the track. This is especially dangerous when skiiing in slopes at high speed. The same disadvantages are connected with the use of non-slipping devices where the connnection of the braking blade is realized using rather bulky fastening elements mounted on top of the ski like the device shown in CH Pat. No. 165 186 (Moser) or extending from the top widely over the sides of the ski as shown in U.S. Pat. No. 2,375,943 (Pape), which elements are fixed to the ski even when the braking element is removed from its working position.
Earlier known non-slipping devices of the type having a blade element pivotally attached to a horizontal axis and extending under the bottom surface of the ski may include an axle system lying either above the upper plane of the skis as is shown in DE Pat. No. 803 282 (Prestel) and CH Pat. No. 165 186 (Moser) or in the sides of the skis as is the case according to CH Pat. No. 336 738 (Chatelain). The solutions according to the above mentioned patents all include such a positioning of the fastening elements that the pivot pins or other contraptions extend outside the sides or the top of the skis. Such a positioning of the axis forms a risk of danger as mentioned previously. Furthermore a positioning of the axis above the top surface of the ski will cause the braking edge of the braking element to move a long way from the position when the ski is running forwards to the braking position. This long movement will make the action of the brake arrangement slow and will bring the braking edge to a position far below the running surface of the ski, which is a great disadvantage on semi-hard surfaces.
A solution with specially designed pivot pins screwable into separate elements such as one of the embodiments shown in DE Pat. No. 803 282 (Prestel) can hardly be used in the conditions generally prevailing at skiing when it is cold, and snow and ice penetrate into the holes and makes it impossible to attach the blade in a simple way. On the other hand complicated fastening methods are impractical in daily use. From the practical point of view it is generally necessary that a blade which is adapted to glide under the running surface of the ski is fastened in such a way that it may easily be removed at need without there existing any risk of the blade falling off by mistake.
Large forces are exerted on the pivot pins during the function of the non-slipping device and it seams unlikely that a fixed pivot which is merely mounted onto a bore in the side of the ski will be kept in place for any longer space of time, especially since such outward extending pivots easily clash against each other at skiing. Moreover a pivot screwed into the side of the ski may weaken the ski considerably. In the construction described in CH Pat. No. 336 738 (Chatelain) the pivot should be attached to the ski already at the production stage, which presumably is one reason as to why the device has not become generally used.
In the prior known non-slipping device solutions having a blade moving under the surface of the ski, the blade is usually stopped in its braking position by the blade edge resting against the bottom surface of the ski. With time such a construction will impair the bottom surface of the ski in the place where the blade edges touches the same, and may even lead to an eventual breaking of the ski.